A typical fuel supply system for a heavy duty vehicle includes several components, including a fuel tank, a fuel supply line for delivering fuel to the engine, a fuel return line for returning excess fuel to the tank that is not required for engine power requirements, and a fuel cooling system for cooling the fuel returned to the tank.
Referring to FIG. 1, a cross-sectional view of a prior art fuel tank 10 for a heavy duty vehicle is depicted. The fuel tank 10 of a heavy duty vehicle is typically configured as a cylindrical tank fabricated from aluminum sheet with welded aluminum ends. Fuel 12 is stored within the tank 10, and it is supplied to the engine via a fuel supply line 14. Excess fuel is returned from the engine through a fuel return line 18. The fuel return line 18 enters the top of the fuel tank 10 and deposits the returned fuel near the bottom of the tank below the fuel level in the tank.
The returned fuel is normally at a higher temperature than the fuel stored within the tank, and the returned fuel causes the bulk temperature of the fuel stored within the tank to increase. In some applications, this increase in fuel temperature can become problematic for efficient engine operation and requires the addition of an active or passive fuel cooler to control fuel temperature delivered to the engine.
An active fuel cooler is typically configured as an assembly separate from the fuel tank, and it often includes separate mounting hardware and fuel piping. The active fuel coolers may be mounted to the engine radiator assembly to take advantage of the existing engine cooling fan. Alternatively, separate cooling fans may be used in conjunction with the active fuel cooler to provide the necessary fuel cooling. As can be appreciated, active fuel coolers increase the cost and complexity of vehicle assembly.
A passive fuel cooler may be defined in part by the fuel tank itself. For instance, the fuel within the tank may be cooled by temperature conductance through the shell of the tank, wherein the heat is released to the surrounding air by convection. However, the fuel level drops in the tank as the fuel is consumed by the engine. As the fuel level drops, the fuel within the tank is less capable of being cooled by the surrounding air due to the reduction in heat transfer area of the tank shell in contact with the fuel.
Thus, it is desired to provide an improved fuel cooler for a vehicle tank having the cooling capabilities of an active fuel cooler and the simplicity of a passive fuel cooler.